Construction machine

1. A construction machine comprising:

an automotive lower traveling structure ( 2 );

an upper revolving structure ( 3 ) rotatably mounted on said lower traveling structure ( 2 );

a working mechanism ( 4 ) provided capable of moving upward/downward on said upper revolving structure ( 3 ); and

a counterweight ( 5 ) provided on the rear side of said upper revolving structure ( 3 ) in order to keep balance with said working mechanism ( 4 ), wherein

said upper revolving structure ( 3 ) is provided with a revolving frame ( 6 ) forming a support structural body, a floor member ( 10 , 31 ) provided on said revolving frame ( 6 ) and having the rear side as a seat base ( 11 , 32 ) on which an operator's seat ( 17 ) is mounted and the front side as a flat-plate shaped footrest area ( 12 , 33 ) on which an operator places a foot, a cab box ( 20 ) provided covering a periphery and an upper part of said floor member ( 10 , 31 ) and forming an occupying space ( 21 ) inside, and an indoor unit ( 22 ) of an air conditioning unit mounted on said floor member ( 10 , 31 ) and supplying sucked air to said occupying space ( 21 ) as conditioning air; characterized in that:

said seat base ( 11 , 32 ) of said floor member ( 10 , 31 ) has a rear surface plate ( 11 C, 32 C) rising from a rear end of said footrest area ( 12 , 33 ) and extending in a left-right direction, an operator's seat mounting plate ( 11 D, 32 D) provided on an upper end of said rear surface plate ( 11 C, 32 C) and extending in the front-rear direction and on which said operator's seat ( 17 ) is mounted, and a duct accommodating space ( 14 , 35 ) formed in the vertical direction among said rear surface plate ( 11 C, 32 C), said operator's seat mounting plate ( 11 D, 32 D), and said footrest area ( 12 , 33 );

an indoor air inlet duct ( 23 , 38 ) having the front surface side opened as a filter fitting hole ( 25 , 40 ) and introducing air in said occupying space ( 21 ) toward said indoor unit ( 22 ) is provided in said duct accommodating space ( 14 , 35 ); and

an indoor air filter ( 26 , 41 ) for catching dusts in the air is provided on said filter fitting hole ( 25 , 40 ) of said indoor air inlet duct ( 23 , 38 ).

2. The construction machine according to claim 1 , wherein said indoor air inlet duct ( 23 , 38 ) is configured such that said indoor air filter ( 26 , 41 ) is mounted vertically so that a sucking surface is oriented perpendicularly.

3. The construction machine according to claim 1 , wherein a left surface plate ( 11 A, 32 A) and a right surface plate ( 11 B, 32 B) supporting both ends in the left-right direction of said operator's seat mounting plate ( 11 D, 32 D) is provided on said seat base ( 11 , 32 ) of said floor member ( 10 , 31 ), respectively; and

said duct accommodating space ( 14 , 35 ) is configured such that the both ends in the left-right direction are closed by each of said side surface plates ( 11 A, 11 B, 32 A, 32 B).

4. The construction machine according to claim 1 , wherein a front cover ( 16 , 37 ) closing said duct accommodating space ( 14 , 35 ) between said footrest area ( 12 , 33 ) and said operator's seat mounting plate ( 11 D, 32 D) and also covering the front side of said indoor air filter ( 26 , 41 ) is provided on the front side of said seat base ( 11 , 32 ); and

an indoor air suction port ( 15 , 36 ) opened in a filter front space portion ( 14 A, 35 A) between a rear surface of said front cover ( 16 , 37 ) and a front surface of said indoor air filter ( 26 , 41 ) is provided on a front end portion ( 11 D 1 , 32 D 1 ) of said operator's seat mounting plate ( 11 D, 32 D), and said indoor air filter ( 26 , 41 ) is configured such that indoor air is made to flow in from said indoor air suction port ( 15 , 36 ) through said filter front space portion ( 14 A, 35 A).

5. The construction machine according to claim 1 , wherein said indoor air inlet duct ( 23 , 38 ) is composed of a hollow box body ( 24 , 39 ) having the inside as a ventilation path and said filter fitting hole ( 25 , 40 ) provided by being opened on a front surface ( 24 A, 39 A) side of said box body ( 24 , 39 ) and on which said indoor air filter ( 26 , 41 ) is mounted; and

an indoor air outlet port ( 24 F, 39 F) of said box body ( 24 , 39 ) is configured to connect to an indoor air inlet duct connecting portion ( 22 B 1 ) of said indoor unit ( 22 ).

6. The construction machine according to claim 1 , wherein said indoor unit ( 22 ) of said air conditioning unit is configured to be mounted on the back surface side of said footrest area ( 12 , 33 ) of said floor member ( 10 , 31 ).

7. The construction machine according to claim 5 , wherein

a reinforcing connecting pipe ( 44 ) for reinforcing said floor member ( 31 ) is provided between a box body ( 39 ) of said indoor air inlet duct ( 38 ) and an indoor air inlet duct connecting portion ( 22 B 1 ) of said indoor unit ( 22 ), and said indoor air inlet duct ( 38 ) is configured to connect to said indoor air inlet duct connecting portion ( 22 B 1 ) of said indoor unit ( 22 ) through said reinforcing connecting pipe ( 44 ).

8. The construction machine according to claim 1 , wherein said upper revolving structure ( 3 ) is formed as a rear small-revolving machine having a revolving radius (R) between a revolving center ( 0 ) with respect to said lower traveling structure ( 2 ) and said counterweight ( 5 ), a prime mover ( 7 ) is provided at a position on the front side of said counterweight ( 5 ) on said upper revolving structure ( 3 ), and said floor member ( 10 , 31 ) is provided on said revolving frame ( 6 ) at a position on the front side of said prime mover ( 7 ).